This invention concerns a method of and an apparatus for continually applying glue to wood chips which have been formed into the shape of a mixture ring. The invention relates, more particularly, to an apparatus for carrying out the method and which has a nearly horizontally arranged, cylindrical mixture container, in which a mixing shaft is arranged, which is provided with mixing tools and is driven at high speed coaxially to the chips, which have been formed into the mixture ring, a mixture feed support at one end of the mixture container, with a mixture outlet support at the other end of the mixture container and with at least one glue supply pipe, which is located on the mixture container, extends from the outside into the mixture container, and has its respective outlet opening inside the mixture container.
The above-mentioned type of method and apparatus is generally known from the German Federal Republic Offenlegungsschrift (Laid-Open Patent Application) No. 2,019,483, which discloses an apparatus for continually applying glue to wood chips. Spray jets are arranged in the mixture container, these jets projecting slightly into the interior of the mixture container. The spray jets are supplied with glue under pressure, which is then sprayed in the same direction into the interior of the mixture container, in which the wood chips move in the form of a ring of mixture material. In order to achieve this, the jets must project tangentially into the mixture container in the direction of rotation of the mixture ring. In order structurally to realize this, a radially extending recess is formed in the interior wall of the mixture container, out of which the respective spray jets project approximately tangentially to the interior wall of the mixture container. In the proximity of such a recess a dead space is thus formed, in which glue and wood chips can become deposited on the wall of the mixture container. These are loosened in an uncontrolled manner in the form of clumps, which leads to operational disturbances or malfunctions in the known apparatus and/or to malfunctions during later further working of the glued wood chips into chip board. Furthermore, the introduction of the glue under pressure to the spray jets can be problematic because an essential proper amount of glue under pressure can only be obtained at a substantial expense.
A mixing apparatus is known from United States Patent No. 3,163,403 for mixing of softener into a mixture of powered substances during formation of plastics, in which spray jets, to which the softener is supplied under pressure, are arranged in the mixture container wall, the outlet surfaces of the jets lying in the surface of the inner wall of the mixture container. This apparatus, however, has not been suitable to be used successfully for gluing wood chips.
The German Federal Republic Offenlegungsschrift (Laid-Open Patent Application) No. 2,134,305 discloses a method and an apparatus of the type described at the outset, in which the glue supply pipes end, together with their outlet openings, in the mixture ring, at a distance from the inner wall of the container. The glue is primarily supplied without pressure. A distinct disadvantage in this known method and apparatus is that the glue supply pipes are subjected to substantial wear by the chips, which move past it at high speed. In addition, glue undesirably collects in the area of these glue supply pipes and hardens, which can lead to operational malfunctions.